Jpegdecoder

[jepler]

Something's wrong with the doc build; I'll get that sorted soon.

Testing file:

Testing code:

import jpegio
import displayio
import adafruit_pycamera
import numpy
cam = adafruit_pycamera.PyCamera()
j = jpegio.JpegDecoder()
with open("test.jpg", "rb") as f: b = f.read()
w, h = j.decode(b, None)
print(w, h)
bm = displayio.Bitmap(w, h, 65535)
j.decode(b, bm)
arr = ulab.numpy.frombuffer(bm, dtype=ulab.numpy.int16)
arr[:] = arr.byteswap()
cam.blit(bm)
while True:
    pass

[jepler]

This ends up NOT using the ROM jpeg decooder, becaues it's an older version, is not header-compatible, and uses RGB888 instead of RGB565 as desired.

it would be nice to eliminate the need to byte-swap the image before merging this, as that'd be an incompatible change.

[jepler]

[tannewt]

Neat! We may want to enable it on more boards in the future so we can display jpegs right off the web.

[jepler]

If we're planning to try incorporating the esp32 jpeg decoder, we may want to hold off on this specific API; the esp32 simd decoder may not support the /2 /4 /8 downsampling; I'm not sure yet.

/8 downsampling is very useful (for thumbnailing photos taken on a camera, it makes the highest resolution downsample to 320x240 or something)! (and downsampling after decoding isn't viable, as the simd decoder only decodes full images, so it would need 10MB+ RAM for the full image).

Setting back to draft, since it shouldn't go in a beta if we don't think the API's settled.

[jepler]

and it needs bitmaps to be 16-aligned which MAY be guaranteed (aren't gc blocks 16-aligned?)

[tannewt]

and it needs bitmaps to be 16-aligned which MAY be guaranteed (aren't gc blocks 16-aligned?)

Ya, python heap is 16 byte aligned on everything but imx. On imx it is 32 byte aligned to match the cache structure.

[tannewt]

/8 downsampling is very useful

I'd leave it since it is useful. You can always raise an error on other implementations if you really need to. Or fall back to the shared implementation.

[tannewt]

Looks good to me. Won't merge since still a draft.

[jepler]

It looks like there are some boards to disable it on for size reasons. After that I think this'll be ready to go.

[tannewt]

No problem. Thanks for turning it on everywhere we can!